Institute of Physicshttp://normandmousseau.com/publications/83.pdfLiquid–liquid phase transition in Stillinger–Weber silicon2269en10.1088/0953-8984/17/15/002It was recently demonstrated that Stillinger–Weber silicon undergoes a liquid–liquid first-order phase transition deep into the supercooled region (Sastry and Angell 2003 Nat. Mater. 2 739). Here we study the effects of perturbations on this phase transition. We show that the order of the liquid–liquid transition changes with negative pressure. We also find that the liquid–liquid transition disappears when the three-body term of the potential is strengthened by as little as 5%. This implies that the details of the potential could affect strongly the nature and even the existence of the liquid–liquid phase.